We plan to study type I diabetic patients with overt nephropathy in a randomized fashion using placebo, aminoguanidine 2 different doses (to interfere with the production of advanced glycosylation in products) and assess the effect of blockage of crosslinking of proteins on the progression of diabetic nephropathy as well as to assess the safety of aminoguanidine in this population of patients. End of study visits were conducted on all subjects in July and August 1998. Subsequently, the protocol was amended to allow eligible subjects the option of continuing to take blinded study medication until March 1999. Subjects who continue to take blinded study drug are being followed every three months for safety evaluations. Final results of the study drug's safety and efficacy are pending.